Your new movie Contagion is about the global outbreak of a deadly virus. Do you use a lot more hand sanitizer now?
During shooting, we talked about buying stock in Purell, but no. I might wash my hands a little more than I used to, but with kids in New York City  where we live  we do a lot of hand washing anyway.

There's also the theory that germs help kids build up their immune systems, right?
Absolutely. The germ part I'm thrilled about. I want my kids' immune systems to be hardy and ready to take things on.

How do you think you'd react to a pandemic in real life?
I have the benefit of knowing the virologist Ian Lipkin, our technical adviser. He's not the guy to talk to if you don't want to get paranoid. He will freak you out. But I would follow his advice during an outbreak.

Do you reckon the U.S. is ready for something like this?
The CDC is full of heroic scientists who are gaming this stuff and building an incredible line of defense. A lot of responsibility would fall on the media to sell calm and reason instead of fear.
(See Richard Corliss' review of Contagion.)

There's a lot of fear in this movie, though. What's the message there?
Hopefully the takeaway is to take a deep breath and count to 10. But I don't go into a movie trying to send a message. Filmmaking is storytelling.

You won an Academy Award in 1998 for writing Good Will Hunting. Why haven't you done more screenplays?
The creative, problem-solving part of myself that I use to write a script  I still get to use that when I'm acting. One of my favorite scenes in Contagion is when I get the news that my wife is dead. That was a rewrite we did on the spot with an ER doctor who's had that conversation hundreds of times.

Why have you chosen to focus on water in your philanthropy?
I met the engineer Gary White, and I was so inspired by his innovations that we founded Water.org He invented WaterCredit, which takes the concepts behind microfinance and applies them to water. Say you live in a slum in India, where a municipality is piping clean water through the neighborhood. For a $75 loan, you can get that water coming directly into your home forever.
(See Matt Damon and Gary White in the 2011 TIME 100.)

At the Save Our Schools rally in Washington, you made comments defending teachers that received a lot of attention.
My mother is a professor of early-childhood education. At the rally, I just wanted to boost teachers' morale because they've been taking a real beating. How many young people are not going into teaching who would have if there was more prestige or if public treatment of teachers was better?

You've been critical of President Obama recently. What kind of leader do we need?
Somebody who believes that building a strong, solid, educated middle class is ultimately the best thing for America. Someone like FDR. There's a misconception that leaders lead. They don't. They follow. Every great movement has come from the bottom up.

Your hometown team, the Boston Red Sox, has the best record in the American League right now. What are their chances this year?
I think we can beat Philadelphia in a seven-game series. But that rotation is pretty daunting.